1. Field of the Invention
The present invention relates to a transfer method, transfer apparatus, and recording medium for transferring, from a master carrier having microscopic asperities formed thereon, one of the asperities and transfer information represented by the asperities onto a slave medium.
2. Description of the Related Art
There has recently been a demand for size reduction and capacity increase in various information recording media such as a magnetic disk, optical disk, and magneto-optical disk. Additionally, the widespread use of mobile terminals and other factors has increased the demand for the downsizing of devices such as an electronic device and optical device and the mass production of the devices. Against this background, for example, recording media have decreased to several tens to hundreds of nm in the track width of recorded recording signal bits, the magnetization reversal interval in a linear recording direction, and the like.
To accurately retrieve information from such a recording medium having a narrow track pitch, it is necessary for a head which reads and writes information to accurately perform scanning within a narrow track width. Servo signals for tracking, address information signals, reproduction clock signals, and the like are preformatted and recorded on a magnetic disk at predetermined intervals to perform tracking servo control for a magnetic head.
Although the recording can also be performed by a magnetic head, batch transfer from a master disk serving as a master carrier having format information and address information written thereon is more efficient and preferable. For example, there is proposed a magnetic transfer method in which a master disk having a magnetic layer with an asperity pattern corresponding to information to be transferred is prepared for a slave disk serving as a slave medium which is a high-density magnetic recording medium, a magnetic layer of the slave disk is initially magnetized in one direction along tracks, and then a transfer magnetic field is applied to the magnetic layer in a direction almost opposite to the initial magnetization direction while the initially magnetized slave disk and master disk are in close contact (see, e.g., Japanese Patent Application Laid-Open No. 2001-14667).
There are problems such as generation of erased noise or crosstalk noise between adjacent tracks caused by an increase in track density and demagnetization due to thermal fluctuation in recording magnetization caused by an increase in linear recording density. To cope with these problems, there are also proposed magnetic recording media of types called discrete track medium and patterned medium.
In a magnetic recording medium of a type called discrete track medium or patterned medium, a surface thereof needs to be patterned into a predetermined shape. In patterning, since microfabrication of the whole of a recording medium is difficult, an imprinting method in which a master disk (stamper) having a predetermined pattern formed thereon is pressed against a slave disk to transfer the pattern on the master disk onto the slave disk is used, as in the mass production of small electronic devices or optical devices.
In any of the above-described recording medium transfer methods, it is important to uniformly press a master disk and slave disk all over the surfaces and bring the disks into close contact with each other. If there is a portion exhibiting poor adhesion, a signal dropout occurs in transferred information, and the signal quality deteriorates. For example, if recorded signals are servo signals, a satisfactory tracking function cannot be obtained, and the reliability decreases. To cope with such a problem, there is proposed a magnetic transfer apparatus holder for holding a master disk which is provided with a shock absorbing material to improve adhesion (see, e.g., Japanese Patent Application Laid-Open No. 2004-86995).
However, there are limits to the machining accuracy of a holder and shock absorbing material in pressing using the holder and shock absorbing material. Accordingly, a master carrier may be deformed at the time of pressing to cause a difference between a pattern on the master carrier and a transferred pattern, depending on the machining accuracy of the members.
Fluid pressurization is conceivable as a method for uniformly pressing a master carrier regardless of machining accuracy. However, even by this method, a master carrier directly pressed by fluid may be deformed. Or, when a master carrier is indirectly pressed through a flexible film which is interposed between the fluid and the master carrier, the flexible film may be deformed, consequently, the master carrier may also be deformed because the deformed flexible film drags the master carrier by friction. Therefore, use of the method without change is difficult.